The present invention relates generally to operations performed and equipment utilized in conjunction with subterranean wells and, in an embodiment described herein, more particularly provides a system for hydraulically controlling actuation of downhole tools.
It is very advantageous to be able to independently control well tools from the earth""s surface, or other remote location. For example, production from one of several zones intersected by a well may be halted due to water invasion, while production continues from the other zones. Alternatively, one zone may be in communication with a production tubing string, while the other zones are shut in.
In order to control multiple downhole well tools, various systems have been proposed and used. One type of system utilizes electrical signals to select from among multiple well tools for operation of the selected tool or tools. Another type of system utilizes pressure pulses on hydraulic lines, with the pulses being counted by the individual tools, to select particular tools for operation thereof.
Unfortunately, these systems suffer from fundamental disadvantages. The systems which use electrical communication or power to select or actuate a downhole tool typically have temperature limitations for electrical circuitry thereof or are prone to conductivity and insulation problems, particularly where integrated circuits are utilized or connectors are exposed to well fluids. The systems which use pressure pulses are typically very complex and, therefore, expensive to manufacture and difficult to maintain.
From the foregoing, it can be seen that it would be quite desirable to provide a well control system which does not use electricity or complex pressure pulse counting mechanisms, but which provides a reliable, simple and cost effective means of controlling downhole tools. It is accordingly an object of the present invention to provide such a well control system and associated methods of controlling well tools.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a well control system is provided which permits convenient control over the actuation of well tool assemblies in a well. The system permits independent control of individual ones of the well tool assemblies. Associated methods are also provided.
In one aspect of the present invention, a system for selectively actuating multiple well tool assemblies is provided. Multiple hydraulic lines are connected to the multiple well tool assemblies, with each of the hydraulic lines being connected to an actuation control module of each of the well tool assemblies. Each control module includes a selecting device and a fluid metering device.
The selecting device compares pressure on one of the hydraulic lines to a reference pressure source. The well tool assembly associated with the selecting device is selected when the pressure on the hydraulic line is greater than the reference pressure by a predetermined amount, but differs from the reference pressure by less than another predetermined amount. The predetermined amounts may be determined by relief valves of the selecting device interconnected between the hydraulic line and the reference pressure source.
The fluid metering device transfers fluid from the hydraulic line to an actuator of the associated well tool assembly in response to alternating pressure increases and decreases on another one of the hydraulic lines. The fluid transferring function is only performed when the well tool assembly is selected.
In another aspect of the present invention, an actuation control module is provided for selectively actuating a well tool assembly in a well. At least two hydraulic lines and a reference pressure source are connected to the control module. A selecting device of the control module includes two valves interconnected in series between one of the hydraulic lines and a fluid metering device of the control module. One of the valves opens when pressure on the hydraulic line is greater than a reference pressure by a first predetermined amount, and the other valve closes when pressure on the hydraulic line is greater than the reference pressure by a second predetermined amount.
The fluid metering device includes two pumps. One of the pumps transfers fluid from a first hydraulic line to an actuator of the well tool assembly in response to fluctuations in pressure on a second hydraulic line, and the other pump transfers fluid from the second hydraulic line to the actuator in response to fluctuations in pressure on the first hydraulic line.
In each case, the fluid is transferred via a different output of the control module, so that the actuator may be operated in a chosen manner by selecting which of the pumps is to be used. Selection of the pump to use is accomplished by merely applying a greater pressure to one of the hydraulic lines as compared to the other hydraulic line after the well tool assembly has been selected.
Each of the pumps includes a metering chamber having a known volume. Thus, a known volume of fluid may be transferred to the actuator, in order to produce a known displacement of a piston of the actuator.
In yet another aspect of the present invention, a method is provided for selectively controlling actuation of multiple well tool assemblies. The method includes the steps of positioning the well tool assemblies in a well; connecting first and second hydraulic lines to each well tool assembly; selecting one of the well tool assemblies for actuation thereof by applying a predetermined pressure to the first and second hydraulic lines; and actuating the selected well tool assembly by applying another greater pressure to one of the hydraulic lines.